The present invention relates generally to electrical connectors and, more particularly, to a jack for multi-conductor cord terminated by a modular plug connector designed to be connected to a printed circuit board.
The termination of multi-conductor cord by modular plug connectors has become commonplace. Examples of such modular plug connectors are disclosed in patents assigned to Western Electric Company, Inc., such as U.S. Pat. Nos. 3,699,498, 3,761,869, 3,860,316 and 3,954,320. Another advantageous configuration of a modular plug connector is disclosed in U.S. Pat. 4,211,462 assigned to Stewart Stamping Corporation, assignee of the instant application. Essentially, the modular plug connector includes a dielectric housing having a cavity into which an end portion of the cord having exposed conductors is received. Flat contact terminals corresponding in number to the number of cord conductors are inserted into respective slots which open at the housing top so that blade-like portions thereof pierce respective cord conductors with straight upper edges of the contact terminal being exposed at the top of the housing adapted to be engaged by respective jack contacts when the modular plug connector is inserted into the jack.
It is frequently necessary to connect a multi-conductor cord terminated by a modular plug connector to a printed circuit board. In this connection, jacks for modular plug connectors have been designed for connection to a printed circuit board.
In particular, conventional jacks of this type, such as those available from Virginia Plastic Company of Roanoke, Virginia, generally comprise a one-piece plastic housing having a longitudinal cavity opening at the front of the housing adapted to receive the modular plug connector. Associated with the housing are a plurality of jack contacts adapted to engage the straight upper edges of the contact terminals of the plug connector when the latter is inserted into the jack receptacle. Each jack contact is held by slots or grooves formed in the housing and includes a portion which extends along the rear housing wall and projects below the bottom of the housing for insertion into the printed circuit board and a portion which extends through a slot formed through the jack housing top wall into the jack receptacle for engagement with the upper edge of a respective contact terminal of the plug connector.
These jacks are not entirely satisfactory for several reasons. For example, the jack contacts are exposed externally of the jack both at the rear as well as at the top wall thereof thus subjecting the contacts to possible damage during use. Moreover, the jack contacts tend to be pushed out or at least become loosened from the slots or grooves which hold them in place due to repeated engagement by the upper edges of the plug connector contact terminals resulting in an unreliable contact engagement. Still further, the jack contacts require several reverse bending operations in manufacture thereby increasing the cost of manufacture of the jack.
Conventional jacks for modular plug connectors designed for connection to a printed circuit board are not completely satisfactory for another reason. Thus, digital-based electronic equipment is a major source of electromagnetic (EMI) and radio frequency (RFI) interference. Such interference has become a problem at least in part due to the movement away from metal and towards plastics as the material from which connector housings are formed. Plastics generally lack the shielding effectiveness inherent in metal housings.
In order to prevent or at least substantially control the emission of interference-causing electromagnetic and radio frequency radiation from multi-conductor cords used in digital-based electronic equipment and to provide at least some protection from interferencecausing signals radiated from external equipment, cords have conventionally be provided with "shielding" in the form of a continuous sheath of conductive material between the outer insulation jacket of the cord and the insulated conductors, the shield surrounding and enclosing the conductors along their length. The shield can be formed of any suitable conductive material such, for example, as thin Mylar having a surface coated with aluminum foil. The shield acts to suppress or contain the interference-causing electromagnetic and radio frequency signals radiating outwardly from the cord conductors and, conversely, to prevent such high frequency signals generated by external equipment from causing interference in the conductors. The shields have conventionally been grounded either by means of a socalled "drain wire" which extends through the cord in electrical engagement with the conductive shield, the end of the drain wire passing out of the connector to be grounded, or by grounding the shield through one of the modular plug connector contacts.
However, these techniques have not satisfactorily eliminated the interference problem and have created additional problems. Specifically, it has been found that there is still a tendency for EMI and RFI to result from the leakage of electromagnetic and radio frequency radiation signals from the cord in the region at which the modular plug connector is inserted into the jack receptacle. Moreover, it is not uncommon for high frequency signals radiated from nearby equipment to pass through the jack and cause interference in the cord conductors.
Furthermore, the radiation shield tends to acquire an electrostatic charge over a period of time. When the radiation shield is grounded using conventional techniques, such as through one of the modular plug connector contacts, it is not uncommon for electrical discharge arcs to occur across the connector contacts or across the printed circuit board conductors. Such arcing can cause serious damage to the electrical equipment.
For these reasons, it has been proposed to modify the modular plug connector by incorporating a shield terminating contact pin as part of the connector itself. In particular, it has been proposed to provide a pin-shaped contact formed of electrically conductive material through a passage formed in a side wall of the modular plug connector so that one end of the contact is exposed externally at one side of the dielectric plug connector housing while a portion of the length of the contact pin electrically engages a region of the foil shield surrounding the conductors. It has been further proposed that a conventional jack be provided with a grounded contact specifically adapted to engage the exposed end of the shield terminating contact pin of the modular plug connector upon its insertion into the jack receptacle to both ground any electrostatic charge in the shield and to conduct the electromagnetic and radio frequency signals carried in the shield to ground thereby preventing leakage of radiation from the connector. In this connection, reference is made to U.S. Pat. Nos. 4,516,825 issued May 14, 1985 and 4,506,944 issued Mar. 26, 1985 and parent application Ser. No. 570,806 filed Jan. 16, 1984, now U.S. Pat. No. 4,537,459, said patents. being assigned to the same assignee as the instant application.
It will be understood that it is desirable to provide a jack for modular plug connectors of the type described above, namely, a plug connector which incorporates a shield terminating contact, which is provided with means for reliably grounding the cord shield through the shield terminating contact of the plug connector upon insertion of the connector into the jack. Moreover, it is also desirable to at the same time provide the jack with effective EMI/RFI shielding characteristics for the modular plug connector itself to suitably attenuate any radiation which may either leak from the region of the connector or be generated by external equipment.